Spin-Glass Behavior in Hole-Doped Lithium Iridates*

Honeycomb iridates have been proposed to host a quantum spin liquid ground state described by the Kitaev model. In these materials, the edge-sharing environment between neighboring isospin-1/2 moments favors strongly anisotropic bond-directional interactions. This creates three orthogonal planes of interaction which cannot be simultaneously satisfied, leading to strong frustration and an emergent spin liquid state. Though most candidate materials order at low temperatures, Kitaev interactions dominate. The three-dimensional β and γ phases of the lithium iridates, Li₂IrO₃, show an unusual incommensurate antiferromagnetic order at T_i~38K. Previous studies have suppressed magnetic order by applying weak magnetic fields and hydrostatic pressure; however, the role that frustration plays in these systems is still debated. Theory predicts that chemical substitution on magnetic sites can induce a spin-glass state in these materials, reflecting frustrated interactions. In this work, we report spin-glass behavior in hole-doped Li₂IrO₃ at low substitution levels, indicating the fragility and tunability of the incommensurate order and indicating the strength frustration.